Animal laughs no joke says expert
These include the panting sounds made by chimps and dogs when they play and chirping sounds observed in rats.
This suggests that the capacity for laughter may be a very ancient emotional response that predates the evolution of humankind, says Panksepp.
Research suggests the capacity for human laughter preceded the capacity for speech.
(old article, I know)
And here's a video of rats giggling when tickled.
Some of you have rats, I believe, do ya'll's rats giggle like that?